Calculate the principal, initial money amount lent, deposited or borrowed in order to earn a due interest of 20,000 units (Dollar, Euro, Pound, etc.), from date: Feb 24, 2019, to date: Feb 24, 2024, namely for a period of 1,826 days (60 Months), with an annual simple flat interest rate of 4.5% if the commission fee (withdrawal) is 0%.

Due interest, I = 20,000


Annual simple interest rate, R = 4.5%


From date: Feb 24, 2019


To date: Feb 24, 2024


Duration, T = 1,826 days (60 Months)


Commission fee (withdrawal), F = 0%


No. of days in a year, N = 365


P = Principal (initial amount):

P = (N × I) ÷ (R × T) =


(365 × 20,000) ÷ (4.5% × 1,826) =


(100 × 365 × 20,000) ÷ (4.5 × 1,826) =


730,000,000 ÷ 8,217 ≈


88,840.209322137033 ≈


88,840.21

B = Amount earned:

B = P + I =


88,840.209322137033 + 20,000 =


108,840.209322137033 ≈


108,840.21

Signs: % percent, ÷ divide, × multiply, = equal, ≈ approximately equal;

Writing numbers: comma ',' as thousands separator; point '.' as a decimal mark;

Calculate principal amount to invest to get a certain simple flat rate interest

Principal = (Number of days in a year × Simple flat rate interest) ÷ (Annual simple flat interest rate × Duration in days)

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All initial amounts of money calculated by users for earning certain simple flat rate interest values


How to calculate the principal - initial amount of money lent, deposited or borrowed in order to collect or pay a simple flat rate due interest by the interest rate, duration and additional fees (transaction fee as withdrawal, payment in advance, etc.).

Annual simple flat rate interest calculation formula:

  • I = S × p% × n

  • I = n years simple interest charged
  • S = initial amount (principal)
  • p% = annual simple flat interest rate (percentage of the principal charged as interest)
  • n = number of years of the lending or borrowing the money
  • Formula for the principal - initial amount of money lent, deposited or borrowed in order to produce a simple flat annual rate:

  • S = I ÷ (p% × n)

Examples of how to calculate the initial amount, the principal, to earn a certain simple flat rate interest:

  • 1) What is the principal that has to be lent, deposited or borrowed for a period of n = 5 years if the simple flat rate interest collected or paid D = 3,500 units, for an annual simple flat interest rate (percentage) p% = 3.5%?
    Answer:
    S = I ÷ (p% × n) = 3,500 ÷ (3.5% × 5) = 3,500 ÷ (3.5/100 × 5) = (3,500 × 100) ÷ (3.5 × 5) = 350,000 ÷ 17.5 = 20,000 units
  • 2) What is the principal that has to be lent, deposited or borrowed for a period of n = 3 years if the simple flat rate interest collected or paid D = 300 units, for an annual simple flat interest rate p% = 2%?
    Answer:
    S = I ÷ (p% × n) = 300 ÷ (2% × 3) = 300 ÷ (2/100 × 3) = (300 × 100) ÷ (2 × 3) = 30,000 ÷ 6 = 5,000 units

Annual simple flat rate interest formula calculated for a period of n years:

  • Principal, S = I ÷ (p% × n)
  • Simple interest, I = S × p% × n
  • Simple flat interest rate, p% = I ÷ (S × n)
  • Number of years for the period of the deposit, lending or borrowing, n = I ÷ (S × p%)

The principal formula for earning an annual simple flat rate interest calculated for a period of m months:

  • Principal, S = (12 × I) ÷ (p% × m)
  • Simple interest, I = (S × p% × m) ÷ 12
  • Interest rate, p% = (12 × I) ÷ (S × m)
  • Number of months of the period, m = (12 × I) ÷ (S × p%)

The principal formula for earning an annual simple flat rate interest calculated for a period of d days:

  • Principal, S = (365 × I) ÷ (p% × d)
  • Simple interest, I = (S × p% × d) ÷ 365
  • Simple interest rate, p% = (365 × I) ÷ (S × d)
  • Number of days of the period, d = (365 × I) ÷ (S × p%)

More examples of how to calculate the principal for earning a simple flat rate interest:

  • 1) Calculate the initial amount S that would generate a simple flat rate interest I = 6.67 units in m = 5 months with a simple interest rate of p% = 4%.
    Answer:
    S = (12 × I) ÷ (p% × m) = (12 × 6.67) ÷ (4% × 5) = (12 × 6.67) ÷ (4/100 × 5) = (100 × 12 × 6.67) ÷ (4 × 5) = (100 × 12 × 6.67) ÷ 20 = 5 × 12 × 6.67 = 400.2 ≈ 400 units
  • 2) Calculate the initial amount that would earn a simple flat rate interest I = 7.5 units in m = 5 months with a simple flat interest rate of p% = 4.5%.
    Answer:
    S = (12 × I) ÷ (p% × m) = (12 × 7.5) ÷ (4.5% × 5) = (100 × 12 × 7.5) ÷ (4.5 × 5) = (100 × 12 × 7.5) ÷ 22.5 = 9,000 ÷ 22.5 = 400 units.